1. Field of the Invention
The present invention relates to hand operated controls for hydraulic devices and particularly to such a device used in conjunction with a hydraulic personnel lifting crane which provides maneuvering of the crane by means of a single operating handle and in which movement of the "bucket" carrying the person is effected by movement of the control handle in the direction of desired movement.
2. Description of the Prior Art
The mobile aerial tower comprises an elongated, articulated arm which can be extended by means of hydraulic cylinders and related linkages and which has a basket or "bucket" fixed to the distal end thereof for the purpose of elevating workers in such applications as the repair of telephone lines, picking fruit, fighting fires, and the like. Such devices have become known, and are commonly referred to as "cherry pickers". Such devices are typically mounted on a vehicle such as a truck and provide a convenient and efficient apparatus which enables workers in various occupations to perform their functions in elevated locations.
The cherry picker is typically provided with a series of switches mounted adjacent the upper periphery of the personnel carrying bucket. These switches are, in turn, connected to one or more hydraulic valves which control the flow or hydraulic fluid to a plurality of cylinders which effect the raising, lowering, and similar movements of the bucket. This of course enables the operator to position himself conveniently to his work and to otherwise control his position while in the bucket.
However, the control switches provided in prior art cherry pickers have comprised a plurality of separate switches, there being a different switch for effecting control of elevation, a second switch for controlling right and left hand movement, and a third switch for effecting forward and reverse movement of the bucket and in some units, a fourth interlock switch for preventing inadvertant movement of the bucket. Reliance on the workers sense of feel is unreliable since the worker is typically wearing heavy work gloves. Accordingly, when utilizing such an arrangement of switches, it is frequently necessary for the operator to remove his eyes from his intended work object to observe the switches and insure that he has selected the proper switch to manipulate the bucket. In the alternative, it is possible for the operator to operate an incorrect one of the switches thereby effecting the movement of the bucket in an undesired direction. This can be not only inconvenient but, in the event that the worker is working adjacent dangerous objects such as high power lines, such inadvert movement can be highly dangerous.